Light-cone coordinates
= Light-cone coordinates
{title2=$x^\pm$}
For mostly-plus signature, $x^+=(x^{D-1}+x^0)/\sqrt2$ and $x^-=(x^{D-1}-x^0)/\sqrt2$ give $ds^2=2dx^+dx^-+dx^Idx^I$. In this convention raising a plus or minus derivative exchanges the two labels.